1. Field of the Invention
This invention relates to improvements in rotating pin tumbler side bar locks and keys therefor.
2. Background and Prior Art
Rotating or twisting tumbler locks with side bar control of the tumblers and keys for operating such locks are well known in the prior art and have been manufactured and sold by Medeco Security Locks, Inc. Of Salem, Va. for over twenty years. Examples are in the following patents assigned to Medeco Security Locks, Inc. U.S. Pat. No. 3,499,302 Spain et al (1970) U.S. Pat. No. 3,722,240 Spain et al (1973), U.S. Pat. No. 4,635,455 Oliver (1987), U.S. Pat. No. 5,289,709 Field (1994), U.S. Pat. No. 5,419,168 Field (1995), U.S. Pat. No. 5,570,601 Field (1996), U.S. Pat. No. 5,615,565 Field (1997) and U.S. Pat. No. 6,023,954 Field (2000).
Security is a necessary feature of a lock and additional security that could be applied to twisting tumbler locks with dual mechanisms would be highly desirable.
A further and extremely desirable feature of a high security lock is the capability for master keying. Providing additional security and utilizing such provision for master keying provides capability for master keyed systems.
It is also advantageous to have a unique key and key blank for locks of the type in order to provide the additional security that key control can accomplish.
This invention relates to improvements to enhance the security of the basic twisting tumbler dual locking mechanism lock known as the Medeco type lock and can be applied to any Medeco type lock with a side bar mechanism including the original Medeco cylinder lock, the Medeco cam lock, the Medeco Biaxial(copyright) lock, and the Medeco Bi-Level(copyright) lock with offset tip tumbler pins. The invention utilizes a sliding member which slides generally axially in the cylinder of the lock and has a projection for contact with an end of a rib on a key blade. The key thus positions the slider which controls the side bar to allow the side bar to move to an unblocked position. The slider control of the side bar and the unique key and key blade provide further degrees of security, allow master keying and key control.